Thermal imaging apparatus which include both infrared (IR) and visible light (VL) camera modules are known in the art. These apparatus allow an operator to capture both an IR image of an object, or scene, of interest and a corresponding VL image, as a control image on which the IR image may be overlaid. These apparatus often include a display screen and the appropriate electronics to map both the IR and VL images to the screen for a concurrent, or fused, display of the images thereon. Because the VL camera module is typically mounted alongside the IR camera module, in these apparatus, such that their respective optical axes are offset from one another, and extend approximately parallel to one another, the parallax phenomena is accounted for when registering one of the images with the other of the images to create a fused image.
Embodiments of such an apparatus, in which optical axes of the IR and VL camera modules are held in fixed relation to one another so that the parallax error is corrected for electronically, via pre-programmed software, when fusing the two images, are described in co-pending and commonly-assigned U.S. patent application 2006/0289772, which is hereby incorporated by reference in its entirety. One example of this type of apparatus is the IR FlexCam®, available from Infrared Solutions, Inc.—a Fluke Company. Although the parallax correction employed by this apparatus provides acceptable fusion of the two images in many situations, there are special situations in which an additional correction is desirable to better register the IR image with the VL image and thereby provide a higher quality fusion.